In order to facilitate communication between communication devices over a network, each network device is typically assigned a unique numeric network address. A user associated with one of the network devices then need only provide the network transport layer with the numeric network address of the intended target to communicate with the target. Although this system functions satisfactorily in small network where users only communicate with a small number of network communication devices, the system cannot be readily transported to large networks since it would require each network user to remember a large number of unique numeric network addresses. For this reason, the domain name system (DNS) was proposed by Mockapetris in 1987 (RFC 1034 and RFC 1035, Network Working Group; presently available at “http://www.ietf.org”) as a mechanism for facilitating communication between communication devices over the Internet.
The DNS facilitates Internet communication by associating domain names with the numeric (IP, “Internet Protocol”) network addresses. The DNS basically consists of resource records, domain name servers, and resolver. Each resource records includes information concerning each network node, including the IP address of the network node, and the domain names associated with the IP address. Together, the resource records provide the Internet with a tree-structured domain name space. Domain name servers are Internet servers which retain information concerning the domain name space. In particular, each domain name server has a file (“zone file”) which retains resource records associated with its own subset of the domain name space. These records are referred to as “authoritative” records. Also, though queries from resolvers, domain name servers also temporarily cache copies of resource records acquired from other domain name servers in order to improve the performance of the retrieval process when non-local data is requested by a resolver. Resolve are local programs which extract information from domain name servers in response to client requests.
Typically, the domain name associated with a network device at particular IP address has a top label field, and one or more lower level label fields. The label fields comprising a domain name are separated from one another through a delimiter (“.”) and are each positioned in the domain name according to their respective relative levels in the domain name hierarchy. To transmit an e-mail message to a recipient having an e-mail account subsisting at a remote network device, using the originator's local computer the originator of the e-mail message provides its e-mail server with the electronic mail message, together with the originator's name, the domain name of the e-mail server in which the originator has established an e-mail account, the recipient's name, and the domain name of the e-mail server in which the recipient has established an e-mail account. In effect, each e-mail account is represented on a e-mail server as a distinct directory, each containing a subdirectory for caching incoming e-mail messages and a sub-directory for caching outgoing e-mail messages.
Upon receipt of the e-mail message from the originator, the originators e-mail server assigns a globally unique message identifier (determined in accordance with the time of receipt of the e-mail message), extracts the domain name of the recipient's e-mail server from the e-mail message, and transmit the extracted domain name to a domain name resolver for determination of the IP address of the recipient's e-mail server. The resolver queries a root DNS server with the top level label identified in the domain name to obtain the IP address of the DNS server which has the zone file associated with the top level domain. The resolver then accesses the identified DNS server using the obtained IP address, and with the label occupying the next highest position in the domain name hierarchy (the label immediately to the left of the top level label in the domain name) obtains the IP address of the DNS server which has the zone file associated with the queried label. The process continues until each label in the domain name has been resolved at which point the last queried DNS server provides the resolver with the IP address of the network device having the specified domain name. The resolver then transmits the received IP address to the originator's e-mail server.
Upon receipt of the IP address assigned to the recipient's e-mail server, the originator's e-mail server establishes a communications channel with the recipients e-mail server and then transmits the e-mail message over the communication channel, typically using Simple Mail Transfer Protocol (commonly referred to as “SMTP”; described in detail in RFC 821 and RFC 1869. “http://www.ietf.org”). After an initial handshaking stage during which the recipient's e-mail server acknowledges that it is willing to receive an e-mail message and that the recipient has established an e-mail account thereon, the originator's e-mail server transmits the e-mail message to the recipient's e-mail server and then closes the communications channel. Upon receipt of the e-mail message, the recipient's e-mail server caches the e-mail message in the directory associated with the recipient.
To retrieve the e-mail message, the recipient establishes a communications channel with the recipient's e-mail server, and retrieves the e-mail message over the communications channel, typically using Post Office Protocol—Version 3 (commonly referred to as “POP3”; described in detail in RFC 1939 and RPC 2449, “http://www.ietf.org”). Again, after an initial handshaking stage, during which the recipient's e-mail server acknowledges that it is ready to transmit e-mail messages to the recipient, the recipient authenticates itself with the e-mail server using an assigned username and password. After the recipient successfully authenticates itself, the recipient is then able to initiate transmission of the e-mail message over the communications channel to the recipient's local computer.
Although e-mail systems have been implemented successfully worldwide, using SMTP and POP3, conventional e-mail systems suffers from at least three main deficiencies. First, the domain names implemented by the DNS must follow the rules for ARPANET host names. Consequently, each domain name label associated with an e-mail server must begin and end with a “letter” or one of the numbers 0 to 9, and contain only “letters”, the numbers 0 to 9 or a hyphen in between. Further, each “letter” can only be one of ‘A’ to ‘Z’ and ‘a’ to ‘z’. As a result, the number of domain names available is severely limited. Second, the DNS system is case insensitive, so that two domain names which have identical spellings but whose component letters do not correspond in terms of their respective cases, will resolve to the same network address. Third, most e-mail servers only accept, for inclusion as part of an e-mail account name, the hyphen, the numbers 0 to 9 and the letters ‘A’ to ‘Z’ and ‘a’ to ‘z’, thereby limiting the number of account names available.
Therefore, there remains a need for an electronic mail system which expands upon the number and type of characters available for the account name component and the domain name component of e-mail addresses.